KR20190098140A - Vehicle braking system and method - Google Patents

Abstract

The vehicle braking device includes a brake pedal 32, a master cylinder 28, and an electronically controlled booster B having an input member and an output member, the output member provided by the driver supplied input force and the electronically controlled booster. It is adapted to provide the master cylinder with an input force combining the boost force. The wheel cylinder 36 is fluidly connected to the outlet of the master cylinder 28 and is operable to provide a wheel braking force proportional to the input force to the master cylinder. The pumps 60-1, 60-2 are operable to pump fluid towards the wheel cylinders to provide auxiliary wheel braking force. The controller 40 is programmed to trigger a hydraulic braking assistance routine in which the pump is activated to provide auxiliary wheel braking force. The controller is programmed to reduce the boost force provided by the electronically controlled booster during the hydraulic braking assistance routine.

Description

Vehicle braking system and method

The present invention relates to vehicle braking systems. In particular, the present invention relates to a vehicle braking system comprising an electronically controlled booster and a method for controlling the electronically controlled booster during operation of the vehicle braking system.

There are various techniques associated with vehicle braking systems and methods.

The present invention provides a vehicle braking system including an electronically controlled booster and a method for controlling the electronically controlled booster during operation of the vehicle braking system, which is an improvement over the prior art.

In one aspect, the present invention provides a vehicle braking system comprising a brake pedal, a master cylinder, and an electronically controlled booster having an input member coupled to the brake pedal and having an output member coupled to the master cylinder. Is adapted to provide the master cylinder with an input force combining the driver supplied input force provided by the input member and the boost force provided by the electronically controlled booster. The wheel cylinder is fluidly connected to the outlet of the master cylinder and is operable to provide wheel braking force proportional to the input force to the master cylinder. The pump is operable to pump fluid towards the wheel cylinders to provide auxiliary wheel braking force. The controller is programmed to trigger a hydraulic braking assist routine in which the pump is activated to provide the auxiliary wheel braking force during fluid communication between the master cylinder outlet and the cylinder. The controller is programmed to reduce the boost force provided by the electronically controlled booster during the hydraulic braking assistance routine.

In another aspect, the present invention provides a method of operating a vehicle braking system. An electronically controlled booster is provided having an input rod coupled to the brake pedal and an output rod coupled to the master cylinder. The driver input supplied to the booster input rod is sensed by the brake pedal. A boost force is provided from the electronically controlled booster to supplement the force supplied by the driver input, such that the boosted output and the boosting force supplied by the driver input to produce a total output force applied to the master cylinder by the booster output rod. The forces are combined. The total output force is transmitted from the master cylinder to the at least one wheel cylinder via hydraulic fluid to provide vehicle braking force. Driver input to the brake pedal is identified as an emergency braking demand. The pump is operated to provide auxiliary wheel braking force to the at least one wheel cylinder in response to identifying the emergency braking request. The electronically controlled booster is operated to reduce the boost force during operation of the pump to provide the auxiliary wheel braking force.

Other aspects of the present invention will become apparent upon consideration of the detailed description and the accompanying drawings.

1 is a schematic diagram of a vehicle braking system according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of an electronically controlled booster selectively coupled between a brake pedal and a master cylinder of the vehicle braking system of FIG. 1. FIG.

Before any embodiments of the present disclosure have been described in detail, the disclosure is not limited to its application to the arrangement of components and the details of construction described in the following detailed description or shown in the following figures. You must understand that. The present disclosure is capable of other embodiments and of being practiced or carried out in various ways.

The vehicle braking system 20 is shown in FIG. 1. The braking system 20 is provided in a vehicle with wheels and has an anti-lock braking function to prevent wheel lockup and skidding during braking at hard braking events or low friction surfaces. -lock braking functionality). The braking system 20 includes a plurality of independent hydraulic braking circuits 26A, 26B between the master cylinder 28 and the plurality of wheel cylinders 36. As described below, the master cylinder 28 can be actuated by a user operable brake pedal 32 together with a booster B. The braking circuits 26A, 26B are physically provided in the hydraulic unit 24. In the illustrated structure, the braking circuits 26A and 26B provide a front / rear split and are coupled to the first or primary circuit 26A and the rear wheels LR, RR coupled to the front wheels LF, RF. Second or secondary circuit 26B. Although the wheel cylinders 36 are shown in FIG. 1 as being coupled with calipers of the disc braking system, other types of hydraulic braking systems may be provided for each wheel. Hydraulic braking circuits can control the selective relief of hydraulic fluid pressure from the wheel cylinders 36 such that the braking force is maintained below the traction limit. A plurality of sensors are coupled to the controller 40 of the braking system 20 to provide input information including wheel speed, pedal movement, circuit fluid pressure, and the like, thereby allowing the controller 40 to control the operation of the hydraulic unit 24. Can be. The hydraulic unit 24 is configured to provide braking force distribution and / or traction control as part of the vehicle's overall electronic stability program (ESP) because many of the same hardware components are already provided by the braking system 20. May be The hydraulic unit 24 can be used in automotive braking systems with anti-lock and other functionality, but its application is not limited to such systems.

As shown in FIG. 1, primary hydraulic braking circuit 26A is inlet line 44 (master cylinder 28) in fluid communication with the outlet of primary chamber C ₁ of master cylinder 28 (FIG. 4). Output line from the primary outlet). Inlet line 44 is pilot valve 48 (e.g., normally-open electromagnetically controlled two-position valve), high pressure switching valve 52 (e.g., normally closed electrons). A two-position valve that is miraculously controlled) and a pressure sensor 54. The outlet of the pilot valve 48 is connected to the front wheel cylinders via respective inlet valves 58 (eg, normally open electromagnetically controlled two-position valves) of the parallel pressure lines 59. 36) on both sides. Each of the front wheel cylinders 36 also pumps 60-1 through each outlet valve 62 (eg, normally closed electromagnetically controlled multi-position valve) of the parallel relief lines 63. ) Is coupled to the suction side. The pump 60-1 may include one or a plurality of pump elements (eg, three elements). The outlet valves 62 may be controlled between the various open positions by the controller 40 to bleed off the pressure from the wheel cylinders 36 which are likely to exceed or deem the traction limit excessive. Can be. The accumulator 64 (eg, low pressure accumulator) is coupled in parallel between the outlet valves 62 and the pump 60-1, and the outlet valve before being removed or returned by the pump 60-1. And receive and temporarily store the fluid from (s) 62. The pump 60-1 is driven by the motor 70. All electronic control valves of the motor 70 and the primary and secondary circuits 26A, 26B together with the booster B may be electrically coupled to the controller 40.

Secondary hydraulic braking circuit 26B outputs from inlet line 80 (secondary outlet of master cylinder 28) in fluid communication with the outlet of secondary chamber C ₂ of master cylinder 28 (FIG. 4). Line). The inlet line 80 is fluidly separated from the inlet line 44 so that the primary and secondary circuits 26A and 26B provide separate and independent braking to each wheel cylinder set (in the structure shown in the drawing). Axle and rear axle). Inlet line 80 is in communication with a isolation valve 84 (eg, a normally open, electromagnetically controlled two-position valve). The outlet of the separation valve 84 is connected to the rear wheel cylinders via respective inlet valves 58 (eg, normally open electromagnetically controlled two-position valves) of the parallel pressure lines 59. 36) on both sides. Each of the rear wheel cylinders 36 also pumps 60-2 through each outlet valve 62 (eg, normally closed electromagnetically controlled multi-position valve) of the parallel relief lines 63. ) Is coupled to the suction side. Pump 60-2 may include one or a plurality of pump elements (eg, three elements). The outlet valves 62 may be controlled between the various open positions by the controller 40 to release pressure from the wheel cylinders 36 that are likely to exceed or deem the traction limit excessive. The pump 60-2 is driven by the motor 70 (for example, driven together with the pump 60-1 of the primary braking circuit 26A). The pressure side of the pump 60-2 is connected to the reservoir R of the master cylinder 28 via a pressure control regulating valve 88 (eg, normally closed electromagnetically controlled multi-position valve) of the return line 90. ) Is combined.

Returning to the master cylinder 28 now, each chamber C ₁ , C ₂ is a variable volume chamber controlled by respective first and second pistons P ₁ , P ₂ . The brake pedal 32 operates the first piston P ₁ through the booster B, which is an electronically controlled booster, as described later. The second piston P ₂ is a floating piston and is operated only indirectly by the movement of the first piston P ₁ . The brake pedal 32 is coupled to the rod 94 referred to herein as a booster input rod which acts as an input member to the booster B, the coupling being directly without an intermediate booster in between. Is connected. The first piston P ₁ is coupled to the rod 95 referred to herein as a booster output rod acting as an output member of the booster B so that the first piston P _{1 is} connected to the booster output rod 95. It moves according to the movement. Booster B is such that the force from actuation of brake pedal 32 under critical or “cut-in” force is applied to booster output rod 95 and first piston P ₁ without additional boost force. Transmitted, so that the force on the booster output rod 95 from the actuation of the brake pedal 32 above the cut-in force forms only a portion of the total force transmitted to the booster output rod 95 and the first piston P ₁ . And booster B provides the rest. To apply booster-assisted braking, the stroke amount of the brake pedal 32 or booster input rod 94 is detected by the pedal shift sensor 74 and reported to the controller 40. do. The corresponding controller output is sent to booster B to apply force to output rod 95 and added to the driver supplied force of booster input rod 94 from brake pedal 32. During the primary or normal operating mode of the vehicle braking system 20, the booster B actively assists the driver in generating fluid pressure in the master cylinder 28, so that the targets in the wheel cylinders 36 are targeted. A braking force is achieved and thus a target vehicle deceleration proportional to the force exerted by the driver. The booster B may operate according to a predetermined algorithm to achieve a predetermined boost factor defined by the total force output from the booster B to the master cylinder in relation to the driver-supplied force.

As shown in FIG. 1 and in more detail in FIG. 2, booster B is capable of being driven by booster motor 97 via booster motor 97, transmission 98, and transmission 98. It may be an electromechanical booster comprising a boost body 99. The boost body 99 is coupled to the booster output rod 95. As shown in FIG. 2, the boost body 99 may be coupled to the output rod 95 through the valve body 100 and an elastomeric reaction disc 102. In the structure shown, the transmission 98 includes a drive screw connected to the output of the booster motor 97 and external threads formed on the boost body 99, but other arrangements are optional. . The return spring 96 biases the booster output rod 95 and thus the boost body 99 away from the master cylinder 28. The cut-in spring 104 is the initial or home position away from the valve body 100 when the booster input rod 94 is not actuated by the brake pedal 32. Bias. In the normal operating mode, the deformation of the cut-in spring 104 causes the booster input rod 94 to contact the center of the elastomeric reaction disk 102 and then transfer the force to the booster output rod 95. On the other hand, the outer periphery of the elastomeric reaction disk 102 is operated by the valve body 100 driven by the booster motor 97 via the booster body 99. The controller 40 may be programmed such that the movement of the valve body 100 follows or tracks the movement of the booster input rod 94. Thus, the boost factor of the booster B can be defined by the ratio of the operating regions of the reaction disk 102. In a back-up or fail-safe operating mode in which booster B is not operable to assist in operating master cylinder 28, booster input rod 94 is adjacent valve body 100 and valve body 100. Activates the booster output rod 95 at least partially.

As described below, the controller 40 may be programmed to control the booster B to adjust the ratio of the force applied to the brake pedal to the force applied to the booster during the braking assistance routine (i.e. reduce the force applied to the booster). Thus, even if a substantial pressure drop occurs in the first master cylinder member C ₁ , a change in the pedal reaction force cannot be perceived by the driver. When the brake pedal 32 is operated by the driver, the controller 40 determines how far the brake pedal 32 is operated and also how quickly the input is supplied to the brake pedal 32. These values can be determined by observing the position or movement of the booster input rod 94 with the pedal movement sensor 74 since the brake pedal 32 and the booster input rod 94 have a predetermined kinematic relationship. The controller 40 may also consider other inputs or factors including, but not limited to, the fluid pressure in the master cylinder 28 or the circuits 26A, 26B, or collision avoidance sensors provided to the vehicle. Based on some or all of these inputs, the controller 40 is programmed to identify and trigger the need for the execution of the hydraulic braking assistance routine, whereby the pump 60-1 is driven by the master cylinder chamber C ₁ and It is operated during fluid communication with each wheel cylinder 36 of the first circuit 26A. In one aspect, the hydraulic braking assistance routine identifies the driver's braking request as a request for urgent braking and at the same time identifies that the driver's input is not sufficient to achieve maximum braking force and deceleration even by boost. May be triggered. Accordingly, the hydraulic braking assistance routine assists normal braking by operating the pump 60-1 to achieve maximum braking force and deceleration. In some configurations, the controller 40 can calculate whether the output from the booster B to the master cylinder 28 can trigger an anti-lock braking action, and when determining that the controller 40 will not be possible. The controller 40 may enact a hydraulic braking assistance routine to place the vehicle braking system 20 in an anti-lock braking operation. In other configurations, the hydraulic braking assistance routine may be triggered when the braking system 20 undergoes a "fade" (ie, reduced mutual friction of brake linings due to overheating) and during the fade. There is a reduction in braking torque associated with a given master cylinder pressure or wheel cylinder force.

When the pump 60-1 is operated during the hydraulic braking assistance routine, the pump 60-1 of the first circuit 26A does not have a direct connection with the fluid reservoir R, so that the pump 60-1 is pumped from the master cylinder chamber C ₁ . The fluid is sucked to the suction side of 60-1. Thus, the hydraulic braking assistance routine reduces the fluid pressure in the chamber C ₁ , which in turn leads to a reduction in the reaction force F _TMC exerted from the fluid inside the master cylinder 28 to the booster output rod 95. The booster output rod 95 may also be advanced further into the master cylinder 28 as fluid is evacuated by the pump 60-1 for supply to the wheel cylinders 36. The opposing force F _OUT exerted by the booster output rod 95 also drops in response to the hydraulic braking assistance routine. In the absence of countermeasures, this results in a sudden drop in reaction force (force equal to and opposite to the input force F _IN of FIG. 2) from the booster input rod 94 to the brake pedal 32, which causes braking to the driver. It gives a feeling of not doing or a lack of contact with the brake pedal 32. Some drivers may also feel that the brake assist remains active even when they are not braking. Required at the forces F _TMC , F _OUT between the master cylinder 28 and the booster output rod 95 without a corresponding decrease in input force F _IN and a corresponding decrease in reaction force on brake pedal 32. To accommodate the reduction, the controller 40 is programmed to reduce the boost force F _BOOST .

The boost force reduction can be calculated to correspond to the pressure drop in the master cylinder 28 such that the hydraulic braking assistance routine cannot be perceived by the driver because the driver maintains the depression of the brake pedal 32. As such, the relative proportion of the total output force F _OUT supplied by the driver actually increases. By making the driver more accountable for the total output to the master cylinder through boost reduction, the hydraulic braking assistance routine allows the brake pedal to remain engaged in the circuit 26A without affecting the sense of the brake pedal 32. The fluid pressure in the circuit 26A can be manipulated. This can give improved driver reliability and satisfaction during hydraulic braking assistance routines and the overall driving experience. The controller 40 is programmed to perform a boost force reduction proportional to the master cylinder pressure reduction within a predetermined range or threshold, such that there is a finite limit or upper limit to the amount that the boost force can be reduced during the hydraulic braking assistance routine. Can be. This limit may ensure that under no circumstances does the booster B operate against the driver input to the brake pedal 32.

Various features and advantages of the disclosure are described in the following claims.

Claims (18)

In a vehicle braking system,
brake pedal;
Master cylinder;
An electronically controlled booster having an input member coupled to the brake pedal and having an output member coupled to the master cylinder, the output member adapted to provide a driver supply input force provided by the input member and a boost force provided by the electronically controlled booster. The electronically controlled booster, adapted to provide a combined input force to the master cylinder;
A wheel cylinder fluidly connected to an outlet of the master cylinder and operable to provide a wheel braking force to the master cylinder in proportion to the input force;
A pump operable to pump fluid towards the wheel cylinder to provide an auxiliary wheel braking force; And
A controller programmed to trigger a hydraulic braking assist routine in which the pump is activated to provide the auxiliary wheel braking force during fluid communication between the master cylinder outlet and the wheel cylinder,
The controller is programmed to reduce the boost force provided by the electronically controlled booster during the hydraulic braking assistance routine. The method of claim 1, wherein the controller,
Based on one or both of the speed and amount of operation of the brake pedal, emergency braking is requested,
When identifying that the input force on the master cylinder is not sufficient to maximize deceleration,
A vehicle braking system programmed to trigger the braking assistance routine. 2. The vehicle braking system of claim 1, wherein the output member of the electronic control booster is coupled to a boost body that is driven by an electric motor to receive the boost force. 4. The vehicle braking system of claim 3, wherein the boost body is arranged concentrically around a valve body in which the input member is slidably received. 2. The vehicle braking system of claim 1, wherein the electronically controlled booster comprises an elastomeric reaction disk, through which both the boost force and the driver supply input force are applied to the output member. The at least one wheel cylinder of claim 1, wherein the wheel cylinder is coupled to the first chamber of the master cylinder by a first fluid circuit, and the vehicle braking system is coupled to the second chamber of the master cylinder by a second fluid circuit. Further comprising an additional wheel cylinder. 7. The vehicle braking system of claim 6, wherein the pump is a first pump and the second fluid circuit comprises a second pump having a suction side coupled to a fluid reservoir. The vehicle braking system of claim 1, wherein the controller is programmed to initiate a reduction in boost force simultaneously with the start of the hydraulic braking assistance routine. The vehicle braking system of claim 1, wherein the controller is programmed to reduce the boost force proportional to a decrease in fluid pressure due to operation of the pump during the hydraulic braking assistance routine. The vehicle braking system of claim 1, wherein the input member of the electronic control booster is directly coupled to the brake pedal without any intermediate booster. In a method of operating a vehicle braking system:
Providing an electronically controlled booster having an input rod coupled to the brake pedal and an output rod coupled to the master cylinder;
Sensing a driver input supplied to the booster input rod by the brake pedal;
The force supplied by the driver input to provide an input force from the electronically controlled booster to supplement the force supplied by the driver input, to produce a total output force applied to the master cylinder by the booster output rod and the The boost force combines;
Delivering vehicle total braking force from the master cylinder to at least one wheel cylinder through hydraulic fluid to provide a vehicle braking force;
Identifying the driver input to the brake pedal as an emergency braking demand;
Operating a pump to provide an auxiliary wheel braking force to the at least one wheel cylinder in response to identifying the emergency braking request; And
Operating the electronically controlled booster to reduce the boost force during operation of the pump to provide the auxiliary wheel braking force. 12. The method of claim 11 wherein the driver input is supplied to the booster input rod by the brake pedal without any intermediate booster. 12. The method of claim 11, wherein the driver input to the brake pedal is identified as an emergency braking request by one or both of the amount of brake pedal depression and the brake pedal application speed. 12. The method of claim 11, further comprising maintaining a constant pedal reaction force at the booster input rod equal to the force supplied by the driver input throughout operation of the pump despite a drop in fluid pressure in the master cylinder. Further comprising, the vehicle braking system operating method. 15. The method of claim 14, wherein the boost force is reduced by an amount proportional to the drop in the fluid pressure in the master cylinder. 12. The method of claim 11, wherein the reduction in boost force begins concurrently with the start of the pump operation. 12. The method of claim 11 wherein the total braking force in the at least one wheel cylinder is increased during the simultaneous pump operation and boost force reduction. 12. The method of claim 11, further comprising limiting the reduction of the boost force to a predetermined maximum amount to ensure that the electronically controlled booster does not operate against the driver input.

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